The Sneak skill affects how hard you are to detect when in Sneak mode (crouching). While the level of your sneak skill is very important, there are many other factors to remaining undetected such as your enemies Perception level, how much weight you're carrying, the weight of the weapon you're holding and how fast or slow you're moving. Also when above ground the light makes you easier to detect.
If you attack an enemy while undetected you'll receive a sneak attack bonus which does double the damage of a critical hit. If you try a sneak attack from long range and miss the enemy will be alerted of your presence, and if your sneak attack doesn't kill your enemy in the first hit no further sneak attack on that enemy will result in a bonus whether the enemy's seen you or not.
While sneaking you can also pickpocket other NPCs. If a pickpocket attempt is detected, that person will automatically take it back, if you fail a pickpocket attempt in front of a large crowd, there's a chance they will all become hostile. If you want an item that an NPC is currently wearing or holding you'll have to reverse-pickpocket them. This means you'll have to add something into their inventory with better stats than the item you want. For example, if an NPC is wearing an armor that you want you'll have to add an armor into their inventory with a higher Damage Resistance than the one their currently wearing. If you did this right they should wearing the armor you added when you come out of pickpocket mode, you can now go back into pickpocket mode and the item you wanted should now be in their inventory.
 Perks that require Sneak skill
- Mister Sandman - Level 10, Science 60.
- Ninja - Level 20, Science 80.
- Silent Running - Level 12, Science 50.
 Increasing Sneak skill
- Thief - Increases Sneak by +5
- Silent Running - Increases Sneak by +10
- Sneak Bobblehead - Sneak +10
- Chinese Army: Special Ops Training Manual - Each book increases Sneak by +1 (+2 if you have the Comprehension perk)
|Fallout 3 Skills|
|• Barter • Big Guns • Energy Weapons • Lockpick • Medicine • Melee Weapons • Repair • Science • Small Guns • Sneak • Speech • Unarmed •|
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